阅读说明：本技术 一种科学注塑可视化技术 (Scientific injection molding visualization technology ) 是由 许刚 于 2018-08-30 设计创作，主要内容包括：本发明提供了一种科学注塑可视化技术,包括设计阶段、试模阶段和量产阶段。设计阶段通过模流分析技术(CAE仿真技术)能够进行产品的结构优化与模具设计的优化。试模阶段利用科学注塑七步法,对注塑工艺参数进行逐步的测试与优化,科学注塑七步法包括粘度曲线测试、模腔平衡测试、压力降测试、工艺窗口测试、浇口冻结测试、锁模力测试和冷却时间测试七个步骤,通过科学注塑七步法,能够得到科学合理的注塑成型工艺参数；还通过分段注塑成型技术,得到体积收缩率更均匀、变形更小、生产更稳定的产品；通过模腔压力温度测量技术,优化注塑成型工艺,对注塑生产进行实时品质监控,从而实现无人自动化注塑生产。(The invention provides a scientific injection molding visualization technology which comprises a design stage, a mold testing stage and a mass production stage. In the design stage, the structure optimization of a product and the optimization of the mold design can be carried out through a mold flow analysis technology (CAE simulation technology). In the mold testing stage, a scientific injection molding seven-step method is used for gradually testing and optimizing injection molding process parameters, the scientific injection molding seven-step method comprises seven steps of viscosity curve testing, mold cavity balance testing, pressure drop testing, process window testing, pouring gate freezing testing, mold locking force testing and cooling time testing, and scientific and reasonable injection molding process parameters can be obtained through the scientific injection molding seven-step method; the product with more uniform volume shrinkage, less deformation and more stable production is obtained by a segmented injection molding technology; by means of a mold cavity pressure and temperature measuring technology, an injection molding process is optimized, and real-time quality monitoring is carried out on injection molding production, so that unmanned automatic injection molding production is achieved.)

1. A scientific injection molding visualization technology comprises an injection molding mold design stage, a mold testing stage and a mass production stage, wherein the mold testing stage utilizes a scientific injection molding seven-step method to gradually test and optimize injection molding process parameters, and the scientific injection molding seven-step method comprises the following steps:

the first step of viscosity curve test, which is to set different injection speeds, obtain a relative viscosity curve by using a relevant formula or table and combine an actual injection speed linearity curve so as to select a reasonable injection speed;

a second step of die cavity balance test, wherein for a die with two or more cavities in one die, the weight difference value of the heaviest product and the lightest product is calculated by injection molding of products with different volume amounts so as to verify the reasonability of die design or processing, and when the die cavity is unbalanced, the product or the die needs to be corrected;

thirdly, testing pressure drop, namely reading the actual injection pressure of the melt passing through a nozzle, a main runner of a mold, a sprue, a flow tail end and the like of the injection molding machine through the feedback of the actual injection pressure of a panel of the injection molding machine, so as to calculate the injection pressure loss on a melt flow path, verify the reasonability of the selection of the diameter of the nozzle of the injection molding machine and the design of a runner system of the mold, and correct the nozzle or the mold of the injection molding machine when the pressure drop is out of tolerance;

step four, testing a process window, namely obtaining a pressure maintaining pressure window by setting the processing temperature range of the melt and the die, wherein the center of the window is the reasonable pressure maintaining pressure, and when the product size is bad, the pressure maintaining pressure or the die needs to be corrected;

fifthly, a gate freezing test is carried out, different pressure maintaining time is set from short to long, the weight of each mould of product is weighed, and when the weight of the product is not changed or is changed slightly, the time is reasonable pressure maintaining time;

sixthly, testing the mold clamping force, namely weighing the weight of each mold product by setting different mold clamping forces from large to small, and when the weight of the product is increased or burrs appear, adding 5 tons of mold clamping force at the moment to obtain the reasonable mold clamping force;

and seventhly, testing the cooling time, namely measuring the size of the product by setting different cooling times from long to short, and when the size of the product changes or the appearance is unacceptable, adding 1 second for the cooling time at the moment to obtain the reasonable mold cooling time.

2. A scientific injection molding process according to claim 1, wherein the design stage utilizes mold flow analysis techniques to optimize the structure of the product and the design of the mold, such as the wall thickness of the product, the runner system of the mold, the cooling system of the mold, etc.

3. A scientific injection molding visualization technology as claimed in claim 1, wherein the mold testing stage further utilizes a segmented injection molding technology to perform segmented control of the injection molding process, one or more filling, one compression, one or more pressure maintaining, to preferentially control the viscosity change of the melt during the injection molding process at a speed, so as to obtain a product with better appearance, more uniform volume shrinkage, less deformation and more stable production.

4. A scientific injection molding visualization technology as claimed in claim 1, wherein the mold testing stage further utilizes a mold cavity pressure and temperature measurement technology to optimize process parameters such as V/P switching position, pressure holding pressure, pressure holding time, etc., and an alarm signal is sent to a lower computer for quality monitoring of injection molding production by monitoring a peak value or an integral value of the mold cavity pressure and temperature.

Technical Field

The invention relates to the technical field of injection molding, in particular to a scientific injection molding visualization technology capable of realizing injection molding automatic production.

Background

At present, technical personnel in the technical field of injection molding mostly adopt the traditional experience, namely a trial and error method, to carry out injection molding production, thereby causing the waste of energy and cost, which is mainly expressed in that:

1. the setting of the injection molding process parameters is only based on experience and is different from person to person, and necessary data support and scientific basis are lacked;

2. the parameters of the injection molding process cannot be optimized, so that the waste of injection molding cost and the reduction of injection molding quality are caused;

3. the traditional master carries a hiking experience inheritance mode, which is not beneficial to the implementation of standardized data production by enterprises;

4. the automatic production of injection molding can not be realized.

Disclosure of Invention

In order to solve the technical problems, the invention provides a scientific injection molding visualization technology, which realizes scientific injection molding automatic production by optimizing the structure of a plastic product and the design of a plastic mold, optimizing injection molding process parameters and monitoring the quality of injection molding production.

In order to achieve the purpose, the technical scheme of the invention is as follows:

a scientific injection molding visualization technology comprises an injection molding mold design stage, a mold testing stage and a mass production stage. In the mold testing stage, a scientific injection molding seven-step method is used for gradually testing and optimizing injection molding process parameters, and the scientific injection molding seven-step method comprises the following steps:

the method comprises the following steps of firstly, testing a viscosity curve, namely obtaining a relative viscosity curve by setting different injection speeds and utilizing a relevant formula or table, and combining an actual injection speed linearity curve so as to select a reasonable injection speed;

and a second step of die cavity balance test, namely calculating the weight difference value of the heaviest product and the lightest product by injection molding of products with different volume quantities for a die with two or more cavities so as to verify the reasonability of die design or processing. When the die cavity is unbalanced, the correction of a product or a die is needed;

and thirdly, testing pressure drop, namely reading the actual injection pressure of the melt passing through the injection machine nozzle, the mold main runner, the sprue, the flow tail end and the like through the feedback of the actual injection pressure of the injection machine panel, so as to calculate the injection pressure loss on the melt flow path and verify the reasonability of the injection machine nozzle diameter selection and the mold runner system design. When the pressure drop is out of tolerance, the nozzle or the die of the injection molding machine needs to be corrected;

and step four, testing a process window, namely obtaining a pressure maintaining pressure window by setting the processing temperature range of the melt and the die, wherein the center of the window is the reasonable pressure maintaining pressure. When the product size is poor, the pressure maintaining pressure or the mould needs to be corrected;

fifthly, a gate freezing test is carried out, different pressure maintaining time is set from short to long, the weight of each mould of product is weighed, and when the weight of the product is not changed or is changed slightly, the time is reasonable pressure maintaining time;

sixthly, testing the mold clamping force, namely weighing the weight of each mold product by setting different mold clamping forces from large to small, and when the weight of the product is increased or burrs appear, adding 5 tons of mold clamping force at the moment to obtain the reasonable mold clamping force;

and seventhly, testing the cooling time, namely measuring the size of the product by setting different cooling times from long to short, and adding 1 second for the cooling time at the moment to obtain the reasonable mold cooling time when the size of the product changes or the appearance is unacceptable.

Further, the design stage utilizes a mold flow analysis technology (CAE simulation technology) to perform structural optimization of the product and optimization of the mold design, such as wall thickness of the product, a runner system of the mold, and a cooling system of the mold.

Furthermore, the mold testing stage also utilizes a segmented injection molding technology to perform segmented control on the injection molding process, one or more segments of filling, one segment of compression and one or more segments of pressure maintaining, and the viscosity change of the melt in the injection molding process is preferentially controlled at a speed, so that a product with better appearance, more uniform volume shrinkage, less deformation and more stable production is obtained.

Furthermore, the mold testing stage also utilizes a mold cavity pressure and temperature measuring technology to optimize a V/P switching position (a position for switching the injection molding from a speed control stage to a pressure control stage), pressure maintaining pressure, pressure maintaining time and the like, and sends an alarm signal to a lower computer for quality monitoring of injection molding production by monitoring a mold cavity pressure and temperature peak value or an integral value and the like, so that unmanned automatic production is realized.

Through the technical scheme, the beneficial effects achieved by the invention are as follows:

1. and optimizing the structure of the product and the design of the mold by a mold flow analysis technology (CAE simulation technology).

2. Scientific and reasonable injection molding process parameters are obtained by a scientific injection molding seven-step method.

3. By the aid of the segmented injection molding technology, products with better appearance, more uniform volume shrinkage, less deformation and more stable quality are obtained.

4. By means of the mold cavity pressure and temperature measuring technology, the injection molding process is optimized, and the quality of injection molding production is monitored in real time, so that unmanned automatic injection molding production is realized.

Drawings

FIG. 1 is a flow chart of a scientific injection molding seven-step method.

FIG. 2 is a graph of experimental data for viscosity curve testing.

Fig. 3 is a viscosity graph for determining an optimal filling time.

Fig. 4 is a graph of experimental data for a mold cavity balance test.

FIG. 5 is a graph showing the effect of product weight on mold cavity balance testing.

Fig. 6 is a graph of experimental data for a pressure drop test.

FIG. 7 is a schematic diagram showing the effect of peak pressure in a pressure drop test.

FIG. 8 is a chart of experimental data for a process window test.

FIG. 9 is a graph showing the dwell pressure versus melt temperature for a process window test.

Fig. 10 is a chart of experimental data showing a process window test for a simplified approach.

Fig. 11 is a graph of experimental data for a gate freeze test.

FIG. 12 is a graph showing the relationship between the weight of a product and the dwell time in a gate freezing test.

Fig. 13 is a graph of experimental data for the clamping force test.

FIG. 14 is a graph showing the relationship between the weight of a product and the clamping force in the clamping force test.

FIG. 15 is a chart of experimental data for the cooling time test.

FIG. 16 is a graph showing the relationship between cooling time and product size in the cooling time test.

FIG. 17 is a schematic diagram of a two-stage injection molding process.

FIG. 18 is a schematic diagram of a three-stage injection molding process.

FIG. 19 is a schematic diagram of a four-stage injection molding process.

FIG. 20 is a schematic view of a multi-stage injection molding process.

FIG. 21 is a graph of cavity pressure temperature.

Detailed Description

The technical solution of the present invention will be clearly and completely described below with reference to the embodiment, which is an example of the injection molding process of the end cap, and the related chart also shows the injection molding process parameters of the end cap.

The scientific injection molding process mainly comprises a design stage, a mold testing stage and a mass production stage:

firstly, a design stage: and optimizing the structure of the product and the design of the mold by using a mold flow analysis technology (CAE simulation technology), such as the wall thickness of the product, a runner system of the mold, a cooling system of the mold and the like. The modular flow analysis technique is a conventional technique and is not described in detail herein.

II, a mold testing stage: the injection molding process and the verification and optimization of the injection mold are carried out by utilizing a scientific injection molding seven-step method, a segmented injection molding technology and a mold cavity pressure and temperature measurement technology.

1. The scientific injection molding seven-step method, as shown in figure 1, comprises 7 steps:

1.1 viscosity curve test: as shown in fig. 2 and 3, by setting different injection speeds, a relative viscosity curve is obtained by using a relevant formula or table, and a reasonable injection speed (the injection speed corresponding to the small viscosity change) is selected by combining an actual injection speed linearity curve. The specific operation method comprises the following steps:

A. the melt temperature was set to the manufacturer's recommended temperature. If it is a range, the temperature is set to the middle value.

B. All the dwell parameters were set to zero, the dwell pressure 0 and the dwell time 0.

C. The injection pressure is set to the maximum available value of the injection molding machine.

D. The cooling time is set to a safe value. In this way the product will be cooled and has reached the ejection temperature before opening the mould.

E. A molded product is molded at a medium-low speed, and the product must be short-shot. If not, the switch (V/P switch) position is adjusted to ensure that the product is only about 50% full.

F. The injection speed was increased stepwise to ensure that the part was still shot short. Until the maximum injection speed of the injection molding machine is approached and it is ensured that the product that is first filled is still shot short (95-99% full of fill). If less than 95% full, then the switch is also adjusted to fill the product to 95-99% full.

G. At this maximum injection speed, another mold was molded and the fill time required at that time and the maximum injection pressure required were recorded.

H. Next, the speed is reduced by a smaller amount, for example from 90% to 80%. Fill time and peak injection pressure were recorded at each speed.

I. The above steps are repeated until you get as low an injection speed as possible. The available injection speed range is divided into 10-12 speed points, yielding as many data points as possible.

J. These values are entered in a table to generate a viscosity curve.

The V/P switching position set by the viscosity curve test is the position when the product is filled by 95-99%, and the reasonable V/P switching position can be found more accurately through the die cavity pressure curve.

1.2 die cavity balance test: as shown in fig. 4 and 5, for a mold with two or more cavities, the weight difference value between the heaviest product and the lightest product is calculated by injection molding of products with different volume amounts, so as to verify the reasonability of mold design or processing. When the mold cavity is not balanced, we need to make product or mold modifications. The specific operation method comprises the following steps:

A. the dwell pressure is set to zero and the dwell time is set to zero.

B. The screw recovery (stock) delay time is set to an approximate value close to the estimated dwell time.

C. The cooling time is set to a safe value to ensure that the product has cooled to the top discharge temperature before opening the mold.

D. The injection speed was set and this value was obtained from the viscosity curve test.

E. The molding was started as in the viscosity curve test for the other settings.

F. The molded product is just short shot by only adjusting the transfer position. If there is a significant cavity imbalance, then the "largest" product should be the very shot. Record the product weight (5 die).

G. And continuously forming the short shot product by changing the switching position. The shaped product was 50% full (5 moulds). The product weight is entered into the worksheet.

In this example, the difference in cavity balance is 33.5% at the maximum, and cavity balance correction is required. The criteria that need to be modified may be adjusted according to the specific requirements of each company or product.

1.3 pressure drop test: as shown in fig. 6 and 7, the actual injection pressure of the melt passing through the injection machine nozzle, the mold main runner, the gate, the flow end and the like is read through the feedback of the actual injection pressure of the injection machine panel, so that the injection pressure loss on the melt flow path is calculated, and the reasonability of the selection of the injection machine nozzle diameter and the design of the mold runner system is verified. When the pressure drop exceeds the tolerance, the nozzle or the mold of the injection molding machine needs to be corrected. The specific operation method comprises the following steps:

A. the machine is set to the maximum available injection pressure.

B. And after the material storage is finished, the injection molding machine performs idle injection once. The required peak pressure is noted.

C. The hot runner system of the mold was formed so that the melt just passed the gate of the hot nozzle and the peak pressure was recorded.

D. And forming the cold runner of the mold, enabling the melt to just reach the initial position of the sprue of the cold runner, and recording the peak pressure.

E. A mold is formed so that the melt has just passed the gate and the peak pressure is recorded.

G. A mold was formed so that the melt just reached the end of the fill and the peak pressure was recorded.

As shown in fig. 7, a portion having a high pressure drop is sought.

1.4 Process Window test: as shown in fig. 8, 9 and 10, by setting the processing temperature range of the melt and the mold recommended by the plastic manufacturer, a pressure holding pressure window is obtained, and the center of the window is the reasonable pressure holding pressure. When the product size is not good, the holding pressure or the die needs to be corrected. The specific operation method comprises the following steps:

in general, for amorphous plastics, a dwell pressure VS melt temperature is required; the dwell pressure VS die temperature is required for the crystalline material to determine the process window. The tests given below are dwell pressure and melt temperature. For dwell and mold temperature, the mold temperature was used instead of the melt temperature.

A. The barrel temperature was set to a lower value (lower limit) of the recommended melt temperature.

B. The injection speed was set and this value was obtained from the viscosity curve test.

C. All dwell times and pressures were set to zero.

D. The cooling time is set to be more than a value normally required. For example, if the estimated cooling time is 10 seconds, the cooling time is set to 20 seconds.

E. Injection is started, and the transfer position is adjusted to ensure that the product is filled to 95-98 percent.

F. The product is molded by about 5-8 moulds, so that the process and the melt are stable.

G. The dwell time is now set to a value confirming that the gate is frozen.

H. The dwell pressure was increased in small increments and the pressure was recorded until an acceptable product was made (no short shots, flash, etc.).

I. Note this pressure as the "low temperature-low pressure" angle.

J. The dwell pressure is further increased in similar increments until unacceptable product build-up, such as product sticking or flashing, warping, etc., is produced.

K. Steps (9) and (10) are repeated, but at a higher value (upper limit) of the recommended melt temperature. The two extreme pressures at this time would be the "high temperature-low pressure" and "high temperature-high pressure" angles.

And L, connecting the four corners to generate a process window or a forming area diagram.

M, the setting process is the center of this window.

1.5 Gate freezing test: as shown in fig. 11 and 12, the weight of each mold product was weighed by setting different dwell times (from short to long). When the weight of the product is not changed or is changed very slightly, the time is the reasonable pressure maintaining time.

The specific operation method comprises the following steps:

A. the injection speed was set and this value was obtained from the viscosity curve test.

B. The process is set at the center of the process window for process window study.

C. A cooling time is set which ensures that the product has cooled before ejection.

D. And reducing the pressure maintaining time to zero, and starting forming. Approximately 5 to 8 molds were formed.

E. The dwell time was increased to 1 second and a mold of product was collected and the product weight was recorded.

F. The dwell time was increased to 2 seconds and a mold of product was collected and the product weight was recorded. Similarly, multiple molds were molded in 1 second increments and the product weight per mold was recorded.

G. A "product weight VS dwell time" plot is plotted, similar to the graph in the picture.

H. The sealing time of the gate is determined. The dwell time is selected from the graph as the time just beyond which the product weight is constant.

The accurate pressure maintaining time can be quickly found through a mold cavity pressure curve, the pressure maintaining time is quicker than a pouring gate freezing test through scientific injection molding, and the mold testing time and the cost are saved. And the pressure maintaining time is prolonged, and the time when the pressure of the die cavity does not change obviously is the optimized pressure maintaining time.

1.6 testing the clamping force: as shown in fig. 13 and 14, the weight of each mold product is weighed by setting different mold clamping forces (from large to small), and when the weight of the product is increased or burrs occur, the mold clamping force at this time is the reasonable mold clamping force. The specific operation method comprises the following steps:

A. and when the screw rod material returning time, the injection speed, the pressure maintaining pressure and the pressure maintaining time are optimal, setting the mold locking force of the injection molding machine to be large enough, molding 3 molds, and recording the weight of each mold product.

B. And sequentially reducing the mold clamping force by 5 tons, forming 3 molds each time, and recording the weight of each mold until the weight of the product is suddenly increased.

And (4) conclusion: when the mold clamping force is 40, burrs appear on the product, so that the optimum mold clamping force is selected to be 45 tons of mold clamping force.

1.7 Cooling time test: as shown in fig. 15 and 16, the size of the product is measured by setting different cooling times (from long to short), and when the size of the product changes or the appearance is not acceptable, the cooling time is the reasonable mold cooling time.

The specific operation method comprises the following steps:

A. each mold 3 was formed with a different cooling time, reducing the cooling time until the appearance of the product was affected.

B. And measuring the critical dimension. The product size, appearance are recorded in the table and the plot of "size versus cooling time" of fig. 15 is plotted.

C. The dimensions of the product formed at each cooling time should be measured 24 hours after the product has been removed from the mould.

D. The data was analyzed to see how critical dimensions were affected by cooling time.

E. The optimum cooling time is determined.

And (4) conclusion: when the cooling time is 6 seconds, the product size and the appearance are not qualified, so that the optimal cooling time is selected to be 7 seconds.

2. The segmented injection molding technology comprises the following steps: the method is characterized in that a technology of sectional control is carried out in the injection molding process, filling (one or more sections), compression and pressure maintaining (one or more sections) are carried out, and the viscosity change of a melt in the injection molding process is controlled preferentially at a speed, so that a product with more uniform volume shrinkage, less deformation and more stable production is obtained.

2.1 two-stage injection molding: as shown in fig. 17, one-stage filling + one-stage pressure holding. And (4) quick filling, and switching the position of the screw when the cavity is filled to 95-99% full. The second stage of dwell is used to complete the compression and dwell.

2.2 three-stage injection moulding: as shown in fig. 18, one-stage filling + one-stage compression + one-stage pressure holding. The mold was filled quickly, with screw position switching. When the cavity is 85-95% full, switch to a slower speed (5-10% filling speed) to speed control the compression stage (second stage speed control). When the compression of the product is finished by switching the cavity pressure or the screw position, the V/P switching enters a pressure maintaining stage (third stage).

2.3 four-stage injection molding: as shown in fig. 19, one-stage filling + one-stage compression + two-stage pressure holding. The mold was filled quickly, with screw position switching. When the cavity is 85-95% full, switch to a slower speed (5-10% filling speed) to speed control the compression stage (second stage speed control). And when the compression of the product is completed by switching the pressure of the cavity or the position of the screw, the V/P switching enters a pressure maintaining stage. And in the pressure maintaining stage, a pressure maintaining mode of constant pressure and attenuated pressure is adopted, so that the volume shrinkage of the product is more uniform, and the deformation of the product is smaller.

2.5 multi-section injection molding: as shown in fig. 20, multi-stage filling + one-stage compression + multi-stage pressure holding. The mould is filled fast to multistage speed, makes the leading edge speed of flow more unanimous, switches with the screw rod position. When the cavity is 85-95% full, the speed is switched to a slower speed (5-10% filling speed) to speed control the compression stage (second stage speed control). And when the compression of the product is completed by switching the pressure of the cavity or the position of the screw rod, the V/P switching enters a pressure maintaining stage. And in the pressure maintaining stage, a pressure maintaining mode of constant pressure and attenuated pressure is adopted, so that the volume shrinkage of the product is more uniform, and the deformation of the product is smaller.

3. The mold cavity pressure and temperature measuring technology comprises the following steps: as shown in fig. 21, the injection molding process is optimized by the mold cavity pressure-temperature curve, and the quality of injection molding production is monitored in real time, so that unmanned automatic injection molding production is realized.

3.1 Using the mold cavity pressure temperature curve, the V/P switching position (position where the injection is switched from the speed control stage to the pressure control stage), the holding pressure, the holding time, etc. can be optimized.

3.2, by utilizing a die cavity pressure temperature curve and monitoring a die cavity pressure temperature peak value or an integral value and the like, an alarm signal is sent to a lower computer such as a manipulator, a robot and the like to carry out quality monitoring of injection molding production, so that unmanned automatic production is realized.

In the design stage, the mold flow analysis technology (CAE simulation technology) is utilized to optimize the structure of the product and the design of the mold, such as the wall thickness of the product, a runner system of the mold, a cooling system of the mold and the like. In the mold testing stage, a scientific injection molding seven-step method, a segmented injection molding technology and a mold cavity pressure and temperature measuring technology are utilized, the scientific injection molding seven-step method is utilized to gradually test and optimize injection molding process parameters, and the traditional method of adjusting the injection molding process parameters by relying on experience is changed; a product with more uniform volume shrinkage rate, less deformation and more stable production is obtained by utilizing a segmented injection molding technology; the mold cavity pressure and temperature measuring technology is utilized, the injection molding process is optimized, and the quality of injection molding production is monitored in real time, so that unmanned automatic injection molding production is realized. The invention utilizes scientific method and modern technology to realize the optimization of plastic product structure and plastic mould design, the optimization of injection molding process parameters and the quality monitoring of injection molding production, thereby improving the product quality, reducing the production cost, improving the technical competitiveness of enterprises and realizing unmanned automatic production.

The foregoing embodiments are merely illustrative of the principles and utilities of the present invention and are not intended to limit the invention. Any person skilled in the art can modify or change the above-mentioned embodiments without departing from the spirit and scope of the present invention. Therefore, it is intended that all equivalent modifications or changes which can be made by those skilled in the art without departing from the spirit and technical idea of the present invention shall be covered by the claims of the present invention.